Performance testing and temperature fluctuations of a 4.5 K@150 mW Joule-Thomson closed cycle cryocooler for space applications

Abstract To meet future space applications, the Shanghai Institute of Technology Physics, Chinese Academy of Sciences (SITP, CAS) has developed a closed cycle Joule-Thomson (JT) cryocooler with a prospect of providing more than hundred milliwatts at liquid helium temperatures. The JT cryocooler is driven by staged efficient valved linear compressors with a pressure rate of 18 (low pressure of 0.1 MPa and high pressure of about 1.8 MPa). The designed mass flow is more than 14.8 mg/s. The preliminary experiment is carried out. A two-stage precooler capable of providing a pre-cooling capacity of about 15 K is used to verify the developed JT cryocooler. The test results show that the cryocooler successfully reached 4.5 K with a cooling power of more than 150 mW. A temperature fluctuation test is carried out. A long-term temperature fluctuation of more than 12 h has been tested. There exists a strong reaction among the temperatures of 4.5 K cold head, the precooling stages, and the ambient environment. The temperature fluctuation at 4.5 K cold head is within 5 mK/10 mins because of the large temperature fluctuation of the selected pre-cooler. The quantitative analysis of the temperature fluctuation of each temperature is discussed. By substituting the pre-cooler to a two-stage pulse tube cryocooler developed in our lab, the expected temperature fluctuation can be restrained to 1 mK@10 min and 5 mK@12 h, which can meet the requirement of future applications.